OFFSET
1,1
LINKS
R. H. Hardin, Table of n, a(n) for n = 1..210
FORMULA
Empirical: a(n) = a(n-1) + 6*a(n-2) - a(n-3) - 15*a(n-4) - 20*a(n-5) + 27*a(n-6) + 53*a(n-7) - 14*a(n-8) - 51*a(n-9) - 45*a(n-10) + 60*a(n-11) + 18*a(n-12) - 18*a(n-13) for n>15.
Empirical g.f.: x*(297 - 112*x - 1708*x^2 - 703*x^3 + 3322*x^4 + 7140*x^5 - 3251*x^6 - 14334*x^7 - 2288*x^8 + 9945*x^9 + 14610*x^10 - 10506*x^11 - 5994*x^12 + 3384*x^13 + 216*x^14) / ((1 - x)*(1 + x - x^2)*(1 - x - x^2)*(1 - 3*x^2)*(1 - 2*x^3)*(1 - 3*x^3)). - Colin Barker, Dec 07 2018
EXAMPLE
Some solutions for n=2:
..0..1..0..0....0..1..1..2....0..1..1..2....0..1..1..2....0..0..1..1
..1..2..1..1....1..0..1..1....2..2..3..3....2..0..0..1....2..2..3..3
..3..3..2..2....3..3..1..3....3..0..0..1....3..4..4..0....4..4..0..0
..4..4..3..4....2..1..1..0....4..4..2..2....1..2..2..4....1..1..2..2
..1..1..4..1....1..2..1..1....1..3..3..0....0..3..3..2....3..3..4..4
CROSSREFS
KEYWORD
nonn
AUTHOR
R. H. Hardin, Dec 25 2014
STATUS
approved